JPS6378188A - Thermal fixing roller for copying machine - Google Patents

Abstract

PURPOSE:To obtain the titled roller capable of making surface temperature distribution of the titled roller uniform by forming a strip-like resistance-heating element on the surface of a cylindrical insulating substrate body in a spiral state, so decreasing gradually the pitch of the element towards the both ends of said element from the center part thereof. CONSTITUTION:The insulating layer 1 is formed on the surface of a pipe P0, and the resistance-heating element 2 is formed on the surface of the insulating layer 1. The element 2 is formed by winding a masking wire such as a metal wire 4 round on the surface of the insulating layer 1 in a spiral state, followed by flame-injecting a resisting material such as nichrome, stainless, nickel, aluminum or aluminum solder by means of thermal spray gun G. When the metal wire 4 is removed from the surface of the roll 10, the resistance-heating element 2 is formed in the spiral state. The closer the pitch of the element 2, namely the pitch P of the metal wire 4, gets to the side part 10b and the end part 10a of the roll from the center part 10c of the roll, the smaller it becomes. Next, an anti-sticking film 3 is formed on the surface of the obtd. roll.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a heat fixing roll used in a copying machine, and more specifically to a heat fixing roll for an electronic copying machine.

BACKGROUND OF THE INVENTION A conventional electronic copying machine is provided with a heat fixing roll for heating and fixing a colored toner and a dry developing agent mainly composed of a resin onto a support.

A conventional heat fixing roll has a heating element provided inside a cylindrical metal support, and the heating element heats the surface of the heat fixing roll.

However, this heating method uses radiant heat from the heating element, so
The heat-up time, that is, the time from when the copying machine is started until the copying machine can be used is long, and takes about 1 to 2 minutes.

Therefore, in order to shorten this heat-up time, a planar heating resistor is provided on the surface of the support, a current is passed from one end to the other, and the Joule heat generated at this time directly heats the roll surface. A heating resistor type heat fixing roll is used.

However, since the thickness of this planar heating element is uniform, the surface temperature distribution in the axial direction of the heat fixing roll is lower at both ends 10a of the roll than at the center 10C, as shown by curve 0 in FIG. .

Therefore, it becomes difficult to obtain a uniform image. Therefore,
Conventionally, the resistor film of the heat fixing roll was formed to a constant thickness.
The temperature distribution is made uniform by scraping off this resistor film near both ends of the roll and increasing the resistance value at that part. (Refer to Japanese Unexamined Patent Publication No. 154476 of 1981) Problems to be Solved by the Invention In the conventional example, it is necessary to scrape off the resistor film near both ends of the roll, but this work is troublesome and takes a lot of time. Since it requires labor, it causes an increase in the cost of the roll.

Furthermore, since the resistor film is thin, for example 50 μm thick, it is extremely difficult to shave this film to a predetermined thickness, and as a result, the temperature distribution on the roll surface tends to be uneven. .

In view of the above circumstances, it is an object of the present invention to make the surface temperature distribution of a heat fixing roll uniform.

Another objective is to obtain a low cost heat fixing roll.

Means for Solving the Problems This invention forms a strip-like heating resistor in a screw shape on the surface of a cylindrical insulating support, and the pitch of the heating resistor is varied from the center of the roll to both ends. The above problem is solved by gradually decreasing the size of the filter.

When a current is passed through the band-shaped heating resistor, the current flows in a spiral shape while heating the resistor due to Joule heat.

At this time, since the resistance value is usually higher at both ends of the roll than at the center, the amount of heat generated is larger at both ends than at the center, and the temperature distribution on the roll surface becomes uniform.

Embodiment One embodiment of the present invention will be described with reference to the accompanying drawings.
In the figure, Po is a metal hollow vibe, and this vibe P0
As shown in FIG. 2, an insulating layer 1 is formed on the surface of the insulating layer 1, and a heating resistor 2 is further formed on the surface of the insulating layer 1.

This insulating layer l is made of alumina (^J220s) or spinel (
^2,03 ・MgO) etc. is formed by plasma spraying, and its thickness is, for example, 20
It is 0 μm.

Further, the heating resistor 2 is formed as follows. First of all,
A masking wire, for example, a metal wire 4, is spirally attached to the surface of the insulating layer 1 as shown in FIG.

As the metal wire 4, for example, an Invar wire with a diameter of 0.6 arm is preferably used in order to prevent thermal expansion of the masking wire during thermal spraying, but a high tension copper wire can also be used.

The pitch P of the metal wire 4 is the center portion 10 of the heat fixing roll 10.
The C1 side portion 10b becomes narrower in the order of the end portion 10a, and for example, the pitch P1 of the end portion 10a is 4 am, and the pitch P2 of the side portion 10b is 5 +1 m.

The pitch PS of the central portion 10c is 6■■.

After winding the metal wire 4 in this way, a resistive material such as nichrome, stainless steel, nickel, etc.
The heating resistor 2 is formed by spraying aluminum or aluminum braze with a thermal spraying gun G.

Aluminum or aluminum solder is ideal as a resistance material because its resistance value does not change due to high temperatures and it is inexpensive. This resistor 2 is in the form of a thin film, and its thickness d is, for example, 40μ■
It is.

In this case, a stable heating resistor can be formed by plasma spraying or arc spraying aluminum with air (see Japanese Patent Application No. 80-181081 or 6G-181082). Note that instead of using the thermal spraying, vapor deposition, sputtering, ion plating, etc. may be used. After that, when the metal wire 4 is removed from the surface of the roll 10, the heating resistor 2 becomes thread-shaped as shown in FIG. The pitch of the heating resistor 2 is t&h9. The pitch P of the metal wires 4 becomes smaller from the central portion 10c to the side portions 10b and 4 portions 10a of the roll.

Next, an anti-adhesion film 3 is formed on the roll surface.
is formed with a film thickness t of, for example, 50 μm using a fluororesin or silicone resin coating.

After this coating is completed, the surface of the anti-adhesion film 3 is polished to make it smooth, and a power supply part 6 is provided at one end of the hollow vibrator Pa, a power supply part F is provided at the other end, and the power supply parts 6 and 7 are connected to heating resistors. Connect to the end of body 2.

Next, to explain the operation of this embodiment, when a current is passed from the power supply part 6 to the heat generating resistor 2, this current flows in the direction of arrow AIO while heating the resistor 2 by Joule heat and reaches the power supply part 7. .

In this way, the roll surface temperature increases due to Joule heat, but the center part 10c, side part to
b. Since the pitch P of the heating resistor 2 becomes narrower in the order of the end portion 10a, that is, the pitch PI of the portion where a high calorific value is required,
Since P2 is smaller than the pitch P3 of other parts, the roll surface temperature becomes uniform over its entire length.

To explain this in detail, if the resistance value R0 is the specific resistance value of the material, ρ is the length of the resistor, and the cross-sectional area of the resistor is S, then the resistance value R is expressed as R-ρ・L/S. .

Here, if the pitch of the heating resistor is P, its thickness is d, and the radius of the insulating layer l is e, then the resistance per unit distance in the roll axis direction is r-ρ・2 8 (1/DJ /(d
・0).

Here, if C is a constant, the resistance value r s+ C/D 2
Therefore, the resistance value r per unit distance in the roll axis direction is inversely proportional to the square of the pitch P of the heating resistors.

Therefore, the pitch P of the resistor 2 is set at the end 10 of the roll lO.
Pitch P1 of a is 4 a+a, pitch P of side part 10b,
5 am, and the pitch P of the center portion 10c.

If 6m+o, then from the above relationship, the ratio of the resistance r is 1 for the end 10a and 0.64 for the side tob. The center portion 10c is 0.44.

Also, according to Joule's law, if the current value is l, the amount of heat generated per unit distance W is W + wl'r, which is proportional to the resistance value r. Heat dissipation from the portion 10a and both side portions 10b is balanced, resulting in a uniform surface temperature distribution in the roll axis direction.

When the roll surface temperature distribution of this embodiment and the conventional example was tested, the results shown in FIG. 8 were obtained. That is, in the conventional example, the curve 0
Therefore, while there is an average temperature difference of 30°C between the roll end portion 10a and the center portion 10c, in this example, the straight line N
Therefore, the temperature of the roll surface bodies 10a to 10c became uniform at 200°C.

Note that one residue (power) is continuously supplied to the heating resistor 2 until the heat-up time, but after that, the necessary roll surface temperature can be maintained even if it is intermittently supplied. If the resistance value of resistor 2 is 10Ω, 10
When charged to 0V, the power consumption is IKW, and the heat-up time to 20°C is 10 seconds, which is significantly shorter than the conventional example.

As a method of forming a strip-shaped heat generating resistor in a screw shape, it is possible to coat the entire surface of the insulating layer of the roll to form a resistive film, and to form spiral grooves in this resistive film. In this method, in order to completely isolate adjacent resistors, it is necessary to form the groove deep, that is, to the extent that it sinks into the insulating layer.

Therefore, if a fluororesin is coated to form an anti-adhesion film thereon, the surface is likely to become uneven or lose its flatness.

Therefore, once a thick anti-adhesion film is formed, its surface must be polished to make it smooth, but this polishing process is
In addition to requiring a lot of time, the expensive anti-adhesion film material is scraped away, which increases the cost of the heat fixing roll.

On the other hand, if the heating resistors are formed as described above, the thickness d can be made thinner, so the grooves M between adjacent resistors 2 become shallower.

Therefore, we coated this with fluororesin to prevent adhesion.
3, the surface tends to become naturally flat, and problems such as the polishing work described above do not occur.

According to experiments, the width m of the groove M is 500 μl or less, for example, 4
00μm and then coated with fluororesin to prevent adhesion with a film thickness of 50μm or less, for example, 40μm.
3 was formed and polished to obtain the surface smoothness necessary to prevent adhesion, the surface became smooth enough to be used without any problems.

Other Embodiments Embodiments of the present invention are not limited to those described above; for example, the band-shaped heating resistor may be formed into a double screw shape.

This embodiment will be explained with reference to FIGS. 4 to 6, and the same reference numerals as in FIGS. 1 to 3 have the same names and functions.

As shown in FIG. 5, a metal wire 4 is wound around the surface of an insulating layer 1 in a double screw shape, aluminum wax is sprayed on top of the wire to form a heating resistor 2, and then the metal wire 4 is removed. The center part 10 of the roll becomes a layered shape as shown in FIG.
The pitches Ps, Pt, P+ from c toward the end 10a
becomes smaller sequentially. As shown in FIG. 4, this resistor 2 consists of an outgoing resistor 2a and a backward resistor 2b, one end of which is electrically connected by a coupling portion 2C.

Next, an anti-adhesion film 3 is formed on the roll surface, and a power supply section 6.7 is provided at one end of the hollow vibrator Pa in order to simplify the wiring inside the copying machine.

Then, the outgoing resistor 2a is connected to the power supply section 6, and the return resistor 2b is connected to the power supply section 7.

When a current is passed from the power supply unit 6 to the outgoing resistor 2a, this current heats the resistor 2a by Joule heat, and
It flows in six directions according to the arrows while generating a magnetic field around it.
It reaches the connecting portion 2c of the resistor 2a.

The current that has reached this coupling portion 2c is turned back here and flows to the return path resistor 2b, generating Joule heat and a magnetic field as described above, while flowing in the direction of arrow A7 and reaching the power feeding portion F.

At this time, since the forward path resistor 2a and the backward path resistor 2b are formed in a double screw shape, the currents flow in opposite directions.

Therefore, the magnetic field around the resistor 2a and the magnetic field around the resistor 2b cancel each other out, so in the end,
The magnetic field of the resistors 2a and 2b, that is, the heating resistor 2, almost disappears.Incidentally, the hollow vibrator P6 of the heat fixing roll
When the strength of the magnetic field was measured at a location 2 cam away from the + insulating layer 1 and the heating resistor 2, the maximum measured value was 9.3 Gauss in the case of the - stacked strip heating resistor. (Gauss), the next was 7.2 Gauss, but in the case of a double screw-shaped heating resistor, the highest measured value was 0.4 Gauss, the next was 0.2 Gauss, and 2 m It was found that the strength of the magnetic field decreased significantly when it was made into a screw shape.

In this embodiment as well, the heating resistors 2m are arranged in the order of the central part 10c, side tab, and first part 10a of the heat fixing roll 10.
, 2b is narrow, so the roll surface temperature is of course uniform over its entire length as in the previous embodiment.

In the above embodiment, the band-shaped heating resistor is directly covered with the anti-adhesion film, but as shown in Fig. 47, an insulation @IN is formed on the surface of the band-shaped heating resistor 2, and an anti-adhesion film is formed on the surface of the heating resistor 2. @3 may also be formed.

In this way, there is insulation between the heating resistor 2 and the adhesion prevention @3.
By forming IN, the anti-adhesion wA3 becomes strong, its surface becomes flat, and electrical safety is improved.

Effects of the Invention In this invention, since the band-shaped heating resistor is formed into a screw shape as described above, by gradually decreasing the pitch of the heating resistor from the center of the roll toward both ends, the resistance at both ends is reduced. The value will be greater than the resistance value in the center.

Therefore, since the amount of heat generated from the center of the roll increases toward the ends, the heat dissipation from both ends is balanced, and the surface temperature distribution in the axial direction of the roll becomes as shown by straight line N in Figure 8. As a result, the entire roll surface has a uniform temperature.

In addition, when the resistance value of the heating resistor is gradually decreased from the center of the roll to both ends, it is only necessary to gradually reduce the pitch of the screw-shaped heating resistors on the wheel, so the manufacturing cost is lower than that of conventional methods. It will be cheaper than.

Furthermore, if a band-shaped heating resistor is formed into a double screw shape, one end of which is electrically connected to each other, and the other end is connected to a separate power supply section, current can be supplied from the power supply section to the heat generation resistor. The current flows back and forth over the roll surface in a spiral manner.

At this time, the magnetic fields generated due to the current flow cancel each other out and disappear, so that there is almost no magnetic field on the surface of the heat fixing roll.

[Brief explanation of the drawing]

Figures 1 to 7 are diagrams showing embodiments of the present invention.
The figure is a plan view, FIG. 2 is a partial enlarged cross-sectional view taken along the line 11-11 in FIG. 1, FIG. 3 is a diagram showing the process of forming the heating resistor, and FIG. Figure N5 is a diagram showing how to wind the metal wire around the support, Figure 6 is a diagram showing the state in which the metal wire is removed after forming the heating resistor, and Figure 7 is a cross section showing another example. FIG. 8, which corresponds to FIG. 2, is a diagram showing the temperature distribution on the roll surface. 1...Insulating layer 2...Heating resistor 10...Heat fixing roll P...
Pitch agent Patent attorney Yu Saifuji (Baka 2
Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A heat fixing roll for a copying machine, characterized in that a band-shaped heating resistor is formed in a screw shape on the surface of a cylindrical insulating support. 2. The heat fixing roll for a copying machine according to claim 1, wherein the insulating support has an insulating layer formed on its surface. 3. The heat fixing roll for a copying machine according to claim 2, wherein the insulating layer is in the form of a thin film. 4. The heat fixing roll for a copying machine according to claim 2, wherein the insulating layer is formed by plasma spraying of alumina or spinel. 5. The heat fixing roll for a copying machine according to claim 1, wherein the width of the band-shaped heat generating resistor is narrower in a portion where a high heat generation amount is required than in other portions. 6. The belt-shaped heating resistor is double screw-shaped, and one end thereof is electrically connected to each other, and the other end is connected to a separate power supply part, respectively. Heat fixing roll for copying machines. 7. The heat fixing roll for a copying machine according to claim 1, wherein the band-shaped heating resistor is in the form of a thin film. 8. The heat fixing roll for a copying machine according to claim 1, wherein the band-shaped heating resistor is formed by thermal spraying a resistive material. 9. The heat fixing roll for a copying machine according to claim 1, wherein the band-shaped heating resistor is formed by plasma spraying or arc spraying of a resistive material. 10. The heat fixing roll for a copying machine according to claim 1, wherein the band-shaped heating resistor is formed by thermally spraying a resistive material in air. 11. A patent characterized in that the band-shaped heating resistor is formed by spirally winding a masking wire around the outer periphery of an insulating support, spraying a resistive material thereon, and then removing the wire. A heat fixing roll for a copying machine according to claim 1. 12. The heat fixing roll for a copying machine according to claim 11, wherein the masking wire is an invar wire or a copper wire. 13. Claims 8, 9, or 1, characterized in that the resistance material is aluminum or aluminum solder.
A heat fixing roll for a copying machine according to item 0. 14. The heat fixing roll for a copying machine according to claim 1, wherein the band-shaped heating resistor is covered with an insulating film. 15. The heat fixing roll for a copying machine according to claim 14, wherein the insulating film is covered with an anti-adhesion film. 16. The heat fixing roll for a copying machine according to claim 1, wherein the band-shaped heating resistor is covered with an anti-adhesion film. 17. The heat fixing roll for a copying machine according to claim 16, wherein the adhesion prevention film is formed by coating with fluororesin or silicone resin. 18. The heat fixing roll for a copying machine according to claim 16, wherein the adhesion prevention film fills the heating resistor groove having a width of 500 μm or less and has a film thickness of 50 μm or less.